The present invention relates to a swing support apparatus for swingably supporting an object, e.g., a heavy object, and an object which has a testing device.
A swing support apparatus according to the present invention swingably supports a heavy object around its rotating shaft. For example, a test system necessitates a swing support apparatus for swingably supporting a testing device around its rotating shaft. As a typical application example, a test system (probe system) for performing a probe test in the field of semiconductors will be described below.
Conventional probe systems continuously perform electrical testing of a large number of IC chips formed on a semiconductor wafer. Generally, the probe system includes a loader unit and a prober unit. The loader unit has a transfer mechanism for transferring semiconductor wafers one by one, which are carried in and out in units of cassettes. The prober unit exchanges semiconductor wafers one by one with the transfer mechanism of the loader unit and performs electrical testing separately or continuously for a plurality of IC chips on a semiconductor wafer. This prober unit constitutes a main body of the probe system for performing a probe test and includes a wafer table, a contact mechanism (probe card), and a test head. The wafer table exchanges semiconductor wafers one by one with the transfer mechanism. The probe card has probe needles for connecting the electrodes or pads of an IC chip or chips on a semiconductor wafer to a test circuit. The test head electrically interfaces the probe card to the test circuit. This test head is fixed to a rotating shaft via a frame for supporting the test head main body and hinges. The test head is supported by the main body so as to turn, e.g., 180.degree., together with and around the rotating shaft, between the probe system main body and a maintenance area.
The test head incorporates a large number of electronic parts for electrically interfacing the probe card to the test circuit. The weight of the test head and its accessaries such as the frame reaches about 30 to 100 kg even if the test head is a small one. A motor is often used to swing the test head around the rotating shaft.
A large driving force is required to swing a heavy object such as the test head of the above conventional probe system. Since not only the motor but also gears for transmitting the driving force of the motor become large, it is necessary to increase the mechanical strength of the driving mechanism constituted by these members. Additionally, to prepare for a case where, e.g., the motor fails, a fall preventing mechanism (U.S. Pat. No. 5,506,512 issued Apr. 9, 1996) for preventing the fall of the test head is provided. This further complicates the structure of the swing support apparatus and increases the cost of the apparatus. Furthermore, it is difficult for the motor to accurately position the test head and bring the test head into contact with the contact mechanism such as a probe card without any overload. Therefore, a mechanically complicated positioning mechanism must be provided in addition to the motor, and this further increases the cost of the apparatus. These problems of positioning and holding are left unsolved.
To solve these problems, the invention proposed (Jpn. Pat. Appln. KOKAI Publication No. 6-11542 issued Jan. 21, 1994) uses a torque reducing means for reducing the torque applied on a rotating shaft by the weight of the test head of the above probe system.
With this prior art, it is possible to reduce the driving force required of the motor, smoothly swing an object to be swingably supported, and control inconveniences caused by the fall of the test head.
The problem of positioning, however, is still left unsolved.